• 한국통신학회논문지
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• 제22권4호
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• pp.675-684
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• 1997

The bit rate control algorithm which is capable of handing scene change is proposed. In MPEG-2 TM5, block variance is used to measure block activity. But block variance is not consistent with human visual system and does not differenciate the distribution of pixel values within the block. In target bit allocation process of TM5, global complexity, obtained by results of previous coded pictures, is used. Since I pictures are spaced relatively far apart, their complexity estimate is not very accurate. In the proposed algorithm local variance is used to measure block activity and detect scene change. Local variance, using deviation from the mean of neighboring pixels, well represents the distribution of pixel values within the block. If scene change is detected, the local variance information is used for target bit allocation process. Allocating target bits for I picture, the average local variance difference between previous and current I picture is considered. The experimental results show that the proposed algorithm can detect scene change very precisely and gives better picture quality and higher PSNR values than MPEG-2 TM5.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.633-634
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• 2006

The current unbalance occurs in an induction motor with the supply of unbalanced voltage. Existence of an current unbalance occurs by various problems at the time of driving by in crease of the noise not to mention output decrease of a motor by increase of a loss. We confirmed how current unbalance occurred by a voltage unbalance because a slip came to change by the driving situation of a subordinate as for the induction motor. We confirmed that case to run to a low slip in a ratio of the same voltage unbalance rate brought a high current unbalance rate.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1925-1933
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• 2017

The brushless DC motor's commutation torque ripple is caused by inconsistency in the rate of phase current change. Thus, a method that considers armature resistance is proposed to modulate phase current. The three-phase control strategy, which involves the "open-phase conduction, off-phase pulse width modulation, and maintained non-commutation phase" technique, is applied during commutation at full-speed segments of the motor. Changes in each phase current are analyzed theoretically by establishing mathematical model based on phase current to determine the relative difference among shutdown phase, duty, and motor operating parameters. The turn-on and turn-off phase current change rates are made to be consistent to ensure less non-commutation phase current ripple, then the torque ripple is inhibited. The simulation results show that the phase commutation current and torque ripple coefficient of the proposed method are reduced from 56.9% and 55.5% to 6.8% and 6.1%, respectively. In the experiment system, the pulsation coefficient of the motor phase current is reduced from 40.0% to 16.7% at low speed and 50.0% to 18.8% at high speed. The simulation and experimental results show that the proposed control method significantly inhibits commutation current and torque in the full section.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.254-256
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• 2009

The performances of proton exchange membrane (PEM) water electrolysis depend on many factors such as materials, geometries, fabrication methods, operating conditions, and so forth. The fabrication method is concerned, membrane electrode assemblies (MEA) are a most important part to show different performances by different fabrication methods. The performance change of PEM water electrolysis was experimentally measured according to the fabrication differences of the anode electrodes. One point of view is the catalyst intrusion rate to the anode gas diffusion layer (GDL), and the other point of view is the catalyst loading distribution in depth of the anode GDL. Results show that the performances of MEA with deep intrusion of the catalysts are better in the range of low current densities but worse at higher current densities. The catalyst loading distribution does not affect significantly to the performance of PEM water electrolyser.

• 신재생에너지
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• 제5권4호
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• pp.75-78
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• 2009

The performances of proton exchange membrane (PEM) water electrolysis depend on many factors such as materials, geometries, fabrication methods, operating conditions, and so forth. The fabrication method is concerned, membrane electrode assemblies (MEA) are a most important part to show different performances by different fabrication methods. The performance change of PEM water electrolysis was experimentally measured according to the fabrication differences of the anode electrodes. One point of view is the catalyst intrusion rate to the anode gas diffusion layer (GDL), and the other point of view is the catalyst loading distribution in depth of the anode GDL. Results show that the performances of MEA with deep intrusion of the catalysts are better in the range of low current densities but worse at higher current densities. The catalyst loading distribution does not affect significantly to the performance of PEM water electrolyser.

• 말소리와 음성과학
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• 제5권4호
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• pp.171-184
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• 2013

This study investigated the devoicing rate of Japanese high vowels, focusing on regional and generational differences by acoustically analyzing vowels from two large speech databases. The first speech database used in this study was collected between 1986 and 1988 from 41 areas (prefectures) which included 607 participants (299 high school students and 308 their grandparents). The second was taken from a 2006-2007 collection from seven areas as a follow-up investigation to the first database consisting of 463 participants ranging in age from 8-90 year olds. The results revealed there is a generational as well as regional difference in the devoicing rate in almost all areas. Based on those results, a new distribution map reflecting a current devoicing rate of the younger generation was presented. Furthermore, by comparing the two data sets, this study confirmed age difference in the devoicing rate is not age-grading but a sound change in progress. This study discusses the social factors for changes in the devoicing rate of some areas and then applies the devoicing rate of five areas to an S-curve model to predict the future devoicing rate.

• KDI Journal of Economic Policy
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• 제41권2호
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• pp.1-39
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• 2019

This paper utilizes a life-cycle overlapping-generations model to quantify the welfare effects of plans to postpone the depletion of the National Pension Fund. In order for the model to incorporate the rapidly changing demographic structure of Korea fully, we build and calibrate a model in transition directly. The model is considered suitable for analyzing the effects of demographic changes on the Korean economy and the effects of plans to change the National Pension System. According to a simulation of the model, to postpone the depletion of the National Pension Fund for 30 years, the premium rate must be increased to 18.3% from the current rate of 9%. By postponing the depletion of the fund reserve, young and future generations gain significantly at the expense of the older generations. The simulation results should be, however, interpreted as meaning that the current system is unjustifiably partial to the older generations. Moreover, given the current premium rate, it is desirable to strengthen the income-redistribution function of the National Pension System.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.874-877
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• 2002

The optogalvanic signals were measured using hollow cathode discharge tube with argon as buffer gas at change of discharge currents. A change of ionization rate due to electron collision causes an increase or decrease of the electric conductivity. This change in electric conductivity generates the optogalvanic signal. We conclude that optogalvanic signal has close relation with the lowest metastable atoms density at low current.

• The Journal of Korean Physical Therapy
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• 제11권2호
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• pp.37-42
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• 1999

The purpose of this study was to determine whether percutaneous interferential current stimulation on thoracic sympathetic ganglia with amplitude modulated frequency (AMF) $90\~100$ bps and subthreshold of muscle contraction for 10 minutes on peripheral blood flow velocity in healthy subjects. Thirty-seven healthy volunteers were assigned randomly into an experimental group (n=25) and a control group (n=12). the experimental group received interferential current stimulation with subthreshold of the muscle contraction of current at AMF $90\~100$ bps on $1st\~5th$ thoracic sympathetic ganglial region for 10 minutes. The control group received same handling and electode placement, but no current was applied. Using a Doppler blood flow meter, the radial arterial blood flow velocities and the pulse raters were determined for two-way analysis of variance for repeated measures on time and group. There were no significant difference between the two groups with respect to the changes in arterial blood flow velocity and pulse rate over the four measurement times. Interferential current stimulation did not change in mean blood flow velocity and pulse rate. We conclude that interferential current stimulation on the thoracic sympathetic ganglia, as used in this study, did not dilate peripheral artery. This results suggests that interferential current stimulation dose not alter the activtiy of sympathetic nerve.

• 수산경영론집
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• 제44권2호
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• pp.1-17
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• 2013

We investigate the appropriateness of the fixed 12% discount rate to be used in estimating the amount of compensation for revoking a license for fishery business by the Enforcement Decree of Fisheries Act in Korea. We also suggest the appropriate discount rate fully reflecting the change of market interest rate in the Korean financial market. The capital asset pricing model, or, CAPM is the best known model of risk and return, and is widely used to estimate the expected rate of return for the risky projects. Even though the CAPM implies that the discount rate or the expected rate of return should change as the related market factors do, the discount rate used to estimate compensation for revoking a license for fishery business remains to be the same 12% rate for the last 15 years by law. During this period, however, the yield to maturity for the 5-year government bonds in Korea has dramatically changed from about 12% to less than 3%. In order to provide the fair compensation for the damages against the coastal fisheries and evaluate the intrinsic value of fishery resources in the coastal areas, we suggest that the appropriate discount rate should be determined by the yield to maturity of the government bonds with 5-year maturity, instead of the current fixed 12% interest rate.